METTL1 and head and neck squamous cell carcinoma: Members of the tRNA m7G methyltransferase complex, METTL1 and its partner WDR4, promoted progression and metastasis of head and neck squamous cell carcinoma (HNSCC) via tRNA m7G methylation, thereby enhancing the translation of a subset of oncogenic mRNAs, including genes involved in the PI3K/AKT/mTOR signaling pathway (Fig. 3d) [222].